1. Field of the Invention
This invention relates to a remote control unmanned boat which can be freely operated by remote control and to a remote control device therefore.
2. Description of the Prior Art
At various scenes, unmanned models which permit free remote control are being utilized.
For the purpose of surveying the conditions of water bottoms and water bodies of seas, lakes, ponds, and rivers, an unmanned boat which is capable of remote control (hereinafter referred to as “remote control unmanned boats”) is used. The remote control unmanned boat is loaded with a sonar and consequently enabled by transmitting an ultrasonic wave toward the water bottom and receiving the ultrasonic wave reflected as by the water bottom to detect the condition of a water bottom or a water body. An operator can operate this remote control unmanned boat from a distant place and survey a water bottom at an expected place. A technique of this system is disclosed in the official gazette of JP-A-HEI 11-350536. This technique enables the survey to be effected at a shoal or a narrow water region which defies approach by a large manned boat even during a foul weather and day and night.
When the remote control unmanned boat of such a construction as described above is operated, however, it does not always follow that the operator will succeed in controlling this remote control unmanned boat. The remote control unmanned boat will be no longer controllable in the following cases, for example, as when the remote control unmanned boat rides over waves and flows to a place too distant to be reached by the electric waves of a remote control device, when the boat body is vigorously tossed by waves and the antenna for receiving the electric waves of the remote control device is broken by collision of the boat against a rock, and when the power source for the remote control unmanned boat is exhausted and prevented from supplying a drive electric power.
In such a case, men are compelled to search for the remote control unmanned boat. The possibility that this search will end in failing to locate and recover the missing boat is not undeniable.